Field of the Invention
The present invention relates to a plugged honeycomb structure for a wall flow type exhaust gas filter, and more particularly, it relates to a plugged honeycomb structure suitably for use in removal of particulate matter included in an exhaust gas from an engine such as a car engine or in purification of a toxic gas of nitrogen oxides and the like.
Description of the Related Art
Internal combustion engines are used as power sources in various industries. On the other hand, an exhaust gas emitted from the internal combustion engine at a time of combustion of fuel includes particulate matter (hereinafter also referred to as “PM”) such as soot or ash together with a toxic gas of nitrogen oxides and the like. In particular, regulations on removal of the PM emitted from a diesel engine have become severe worldwide, and a wall flow type gas purifying filter having a honeycomb structure is used as a diesel particulate filter which removes the PM (hereinafter also referred to as “DPF”). Further, as the wall flow type gas purifying filter, there is used a plugged honeycomb structure including a honeycomb structure body in which porous partition walls define a plurality of cells forming through channels for fluid, and plugging portions each of which is disposed in one of open ends of each cell.
The plugged honeycomb structure has a structure in which the porous partition walls constituting the honeycomb structure body perform a function of the PM removing filter. Specifically, in the plugged honeycomb structure, the exhaust gas containing the PM flows into an inflow side end face of the structure, the porous partition walls trap and filter the PM, and then the purified exhaust gas is emitted from an outflow side end face, whereby the plugged honeycomb structure has been used as the DPF.
Heretofore, as this plugged honeycomb structure, a structure has been suggested in which reinforcing portions constituted of R-parts or the like are selectively disposed in corners of the cells defined by the partition walls. For example, a honeycomb structure has been suggested in which substantially circular R-parts are disposed in all intersection portions of the partition walls which have become thin, so that it is possible to prevent generation of cracks (Patent Document 1). Additionally, it has been suggested that substantially circular R-parts are disposed in corners of each cell which face each other, thereby preventing generation of cracks in intersection portions of partition walls (Patent Document 2). The reinforcing portions constituted of the R-parts or the like are basically arranged in all the corners of the cells formed in the plugged honeycomb structure, and additionally, the reinforcing portions have been arranged selectively in the cells formed in a circumferential portion of the honeycomb structure, or the reinforcing portions have been arranged to become larger toward a circumference of the structure.
[Patent Document 1] JP-A-2014-200741
[Patent Document 2] JP-A-2003-269131